Helmet with multiple protective zones

ABSTRACT

The present invention is a protective helmet having multiple zones of protection suitable for use in construction work, athletic endeavors, and similar activities. The helmet includes a hard outer protective that is suspended over a hard anchor zone by elastic cords extending between an elastomeric zone between the outer and inner zones. Fluid filed bladders are positioned in the elastomeric zone and bulge through one or more of a plurality of apertures located in the outer zone. In one embodiment, an additional crumple zone is present. The structure enables the helmet to divert linear and rotational forces away from the user&#39;s braincase.

FIELD OF THE INVENTION

The invention relates to protective headgear, more particularly to sports or work place protective headgear, and still more particularly, to protective headgear designed to prevent or reduce head injury caused by linear or rotational forces.

BACKGROUND OF THE INVENTION

The human brain is an exceedingly delicate structure protected by a series of envelopes to shield it from injury. The innermost layer, the pia mater, covers the surface of the brain. Next to the pia mater is the arachnoid layer, a spidery web-like membrane that acts like a waterproof membrane. Finally, the dura mater, a tough leather like layer, covers the arachnoid layer and adheres to the bones of the skull.

While this structure protects against penetrating trauma because of the bones of the skull, the softer inner layers absorb too little energy before the force is transmitted to the brain itself. Additionally, while the skull may dampen some of the linear force applied to the head, it does nothing to mitigate the effects of angular forces that impart rotational spin to the head. Many surgeons in the field believe the angular or rotational forces applied to the brain are more hazardous than direct linear forces due to the twisting or shear forces they apply to the white matter tracts and the brain stem itself. In addition, because the person's head and the colliding object (including another person's head) are moving independently and in different angles, angular forces, as well as linear forces, are almost always involved in head injuries.

Mild traumatic brain injury (MTBI), more commonly known as “concussion,” is a type of brain injury that occurs frequently in many settings such as construction worksites, manufacturing sites, and athletic endeavors and is particularly problematic in contact sports. While at one time concussion was viewed as a trivial and reversible brain injury, it has become apparent that repetitive concussions, even without loss of consciousness, are serious deleterious events that contribute to debilitating disease processes such as dementia and neuro-degenerative diseases for example Parkinson's disease, chronic traumatic encephalopathy (CTE), and pugilistic dementias.

U.S. Pat. No. 5,815,846 by Calonge describes a helmet with fluid filled chambers that dissipate force by squeezing fluid into adjacent equalization pockets when external force is applied. In such a scenario, energy is dissipated only through viscous friction as fluid is restrictively transferred from one pocket to another. Energy dissipation in this scenario is inversely proportional to the size of the hole between the full pocket and the empty pocket. That is to say, the smaller the hole, the greater the energy drop. The problem with this design is that, as the size of the hole is decreased and the energy dissipation increases, the time to dissipate the energy also increases. Because fluid filled chambers react hydraulically, energy transfer is in essence instantaneous, hence, in the Cologne design, substantial energy is transferred to the brain before viscous fluid can be displaced negating a large portion of the protective function provided by the fluid filled chambers. Viscous friction is too slow an energy dissipating modification to adequately mitigate concussive force. If one were to displace water from a squeeze bottle one can get an idea as to the function of time and force required to displace any fluid when the size of the exit hole is varied. The smaller the transit hole, the greater the force required and the longer the time required for any given force to displace fluid.

U.S. Pat. No. 6,658,671 to Holst discloses a helmet with an inner and outer shell with a sliding layer in between. The sliding layer allows for the displacement of the outer shell relative to the inner shell to help dissipate some of the angular force during a collision applied to the helmet. However, the force dissipation is confined to the outer shell of the helmet. In addition, the Holst helmet provides no mechanism to return the two shells to the resting position relative to each other. A similar shortcoming is seen in the helmet disclosed in U.S. Pat. No. 5,596,777 to Popovich and European patent publication EP 0048442 to Kalman, et al.

German Patent DE 19544375 to Zhan discloses a construction helmet that includes apertures in the hard outer shell that allows the expansion of what appears to be a foam inner liner through the apertures to dispel some of the force of a collision. However, because the inner liner appears to rest against the user's head, some force will be directed toward rather than away from the head. In addition, there is no mechanism to return the expanded foam liner back to the inside of the helmet.

Clearly to prevent traumatic brain injury, not only must penetrating objects be stopped, but any force, angular or linear, imparted to the exterior of the helmet must also be prevented from simply being transmitted to the enclosed skull and brain. That is to say that the helmet must not merely play a passive role in dampening such external forces, but must play an active role in dissipating both linear and angular momentum imparted by said forces such that they have little or no deleterious effect on the delicate brain.

To achieve these ends one must conceive of the helmet much as biologic evolution has of the skull and the brain. That is to say, to afford maximal protection from linear and angular forces, the skull and the brain must be capable of movement independent of each other, and to have mechanisms which dissipate imparted kinetic energy, regardless of the vector or vectors by which it is applied.

To attain these objectives in a helmet design, the inner component (shell) and the outer component (shell or shells) must be capable of appreciable degrees of movement independent of each other. Additionally, the momentum imparted to the outer shell should both be directed away from and/or around the underlying inner shell and brain and sufficiently dissipated so as to negate deleterious effects.

Clearly, there is a need in the art and science of protective head gear design to mitigate these deleterious consequences of repetitive traumatic brain injury.

SUMMARY OF THE INVENTION

The present invention broadly comprises a protective helmet that includes a hard outer shell said hard outer shell including a plurality of apertures; a hard inner shell; a padded inner liner functionally attached to said hard inner shell; a plurality of fluid-filled bladders positioned between said outer shell and said padded inner liner; and, a plurality of elastomeric cords connecting said outer shell and said inner liner.

In an alternate embodiment, the present invention includes a hard outer shell said hard outer shell including a plurality of apertures; a hard inner shell; a padded inner liner functionally attached to said hard inner shell; an intermediate shell contacting said padded inner liner and enclosing a quantity of cushioning pieces; a plurality of fluid-filled bladders positioned between said outer shell and said padded inner liner; and, a plurality of elastomeric cords connecting said outer shell and said inner liner and passing through said intermediate shell.

One object of the invention is to provide a helmet that will direct linear and rotational forces away from the braincase.

A second object of the invention is to supply a helmet that includes an outer shell that floats or is suspended above the inner shell.

A third object of the invention is to offer a helmet with a sliding connection between the inner and outer shells.

An additional object of the invention is to supply a helmet that includes a crumple zone to absorb forces before they reach the braincase of the user.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The nature and mode of the operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing Figures, in which:

FIG. 1 is a front view of the double shell helmet (“helmet”) of the present invention;

FIG. 2 is a side view of the helmet showing two face protection device attachments on one side of the helmet;

FIG. 3 is a cross section view of the helmet showing the inner shell and the elastomeric cords connecting the two shells;

FIG. 3A is a cross section view similar to FIG. 3 depicting an alternate embodiment of the helmet to include an intermediate shell enclosing cushioning pieces;

FIG. 4 is a top perspective view of one section of the outer shell of the helmet showing an alternate embodiment including a liftable lid that protect the diaphragms covering apertures in the outer shell of the helmet;

FIG. 4A is a the same view as FIG. 4 depicting the liftable lid protecting the bulging fluid-filled bladder;

FIG. 5 is an exploded view showing the attachment of the cord to both the inner shell and outer shell to enable the outer shell to float around the inner shell; and,

FIG. 5A is a cross section of the completed cord fitting in which the cord is attached to two plugs and extends between the outer shell and the inner shell.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical structural elements of the invention. It also should be appreciated that figure proportions and angles are not always to scale in order to clearly portray the attributes of the present invention.

While the present invention is described with respect to what is presently considered to be the preferred embodiments, it is understood that the invention is not limited to the disclosed embodiments. The present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. It should be appreciated that the term “substantially” is synonymous with terms such as “nearly”, “very nearly”, “about”, “approximately”, “around”, “bordering on”, “close to”, “essentially”, “in the neighborhood of”, “in the vicinity of”, etc., and such terms may be used interchangeably as appearing in the specification and claims. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described. It should be appreciated that the term “proximate” is synonymous with terms such as “nearby”, “close”, “adjacent”, “neighboring”, “immediate”, “adjoining”, etc., and such terms may be used interchangeably as appearing in the specification and claims.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described.

In the present invention, a helmet is presented that includes multiple protective zones formed in layers over the user's skull or braincase. The outer protective zone is formed by an outer shell that “floats” or is suspended on the inner shell such that rotational force applied to the outer shell will cause it to rotate, or translate around the inner shell rather than immediately transfer such rotational or translational force to the skull and brain.

The inner shell and outer shell are connected to each other by elastomeric cords that serve to limit the rotation of the outer shell on the inner shell and to dissipate energy by virtue of elastic deformation rather than passively transferring rotational force to the brain as with existing helmets. In effect, these elastomeric cords function like mini bungee cords that dissipate both angular and linear forces through a mechanism known as hysteretic damping i.e. when elastomeric cords are deformed, internal friction causes high energy losses to occur. These elastomeric cords are of particular value in preventing so called contrecoup brain injury.

The outer shell, in turn floats on the inner shell by virtue of one or more fluid filled bladders located between the inner shell and the outer shell. To maximize the instantaneous reduction or dissipation of a linear and/or angular force applied to the outer shell, the fluid filled bladders interposed between the hard inner and outer shells may be intimately associated with, that is located under, one or more apertures in the outer shell with the apertures preferably being covered with elastomeric diaphragms and serving to dissipate energy by bulging outward against the elastomeric diaphragm whenever the outer shell is accelerated, by any force vector, toward the inner shell. Alternatively, the diaphragms could be located internally between inner and outer shells, or at the inferior border of the inner and outer shells, if it is imperative to preserve surface continuity in the outer shell. This iteration would necessitate separation between adjacent bladders to allow adequate movement of associated diaphragms.

In existing fluid filled designs, when the outer shell of a helmet receives a linear force that accelerates it toward the inner shell, the interposed gas or fluid is compressed and displaced. Because gas and especially fluid is not readily compressible, it passes the force passively to the inner shell and hence to the skull and the brain. This is indeed the very mechanism by which existing fluid filled helmets fail. The transfer of force is hydraulic and essentially instantaneous, negating the effectiveness of viscous fluid transfers as a means of dissipating concussive force.

Because of the elastomeric diaphragms in the present invention, any force imparted to the outer shell will transfer to the gas or liquid in the bladders, which in turn will instantaneously transfer the force to the external elastomeric diaphragms covering the apertures in the outer shell. The elastomeric diaphragms in turn will bulge out through the aperture in the outer shell, or at the inferior junction between inner and outer shells thereby dissipating the applied force through elastic deformation at the site of the diaphragm rather than passively transferring it to the padded lining of the inner shell. This process directs energy away from the brain and dissipates it via a combination of elastic deformation and tympanic resonance or oscillation. By oscillating, an elastic diaphragm employs the principle of hysteretic damping over and over, thereby maximizing the conversion of kinetic energy to low level heat, which in turn is dissipated harmlessly to the surrounding air.

Furthermore, the elastomeric springs or cords that bridge the space holding the fluid filled bladders (like the arachnoid membrane in the brain) serve to stabilize the spatial relationship of the inner and outer shells and provide additional dissipation of concussive force via the same principle of elastic deformation via the mechanism of stretching, torsion and even compression of the elastic cords.

By combining the bridging effects of the elastic springs or cords as well as the elastomeric diaphragms strategically placed at external apertures, both linear and rotational forces can be effectively dissipated.

Henceforth, my design, by employing elastomeric cords and diaphragms can protect against concussion as well as so called coup and contrecoup brain injury and torsional brain injury which can cause subdural hematoma by tearing of bridging veins or injury to the brain stem through twisting of the stem about its central axis.

Adverting to the drawings, FIG. 1 is a front view of multiple protective zone helmet 10 (“helmet 10”). The outer protective zone is formed by outer shell 12 and is preferably manufactured from rigid, impact resistant materials such as metals, plastics such as polycarbonates, ceramics, composites and similar materials well known to those having skill in the art. Outer shell 12 defines at least one and preferably a plurality of apertures 14. Apertures 14 may be open but are preferably covered by a flexible elastomeric material in the form of diaphragm 16. In a preferred embodiment, helmet 10 also includes several face protection device attachments 18. In a more preferred embodiment, face protection device attachments 18 are fabricated from a flexible elastomeric material to provide flexibility to the attachment. The elastomeric material reduces the rotational pull on helmet 10 if the attached face protection device (not seen in FIG. 1) is pulled. By elastomeric is meant any of various substances resembling rubber in properties, such as resilience and flexibility. Such elastomeric materials are well known to those having skill in the art. FIG. 2 is a side view of helmet 10 showing two face protection device attachments 18 a and 18 b on one side of the helmet. Examples of face protection devices are visors and face masks. Such attachments can also be used for chin straps releasably attached to the helmet in a known manner.

FIG. 3 is a cross section view of helmet 10 showing the hard inner shell 20 and the elastomeric springs or cords 30 (“cords 30”) that extend through an elastomeric zone connecting the two shells. Inner shell 20 forms an anchor zone and is preferably manufactured from rigid, impact resistant materials such as metals, plastics such as polycarbonates, ceramics, composites and similar materials well known to those having skill in the art. Inner shell 20 and outer shell 12 are slidingly connected at sliding connection 22. By slidingly connected is meant that the edges of inner shell 20 and outer shell 12, respectively, slide against or over each other at connection 22. In an alternate embodiment, outer shell 12 and inner shell 20 are connected by an elastomeric element, for example a u-shaped elastomeric connector 22 a (“connector 22 a”). Sliding connection 22 and connector 22 a each serve to both dissipate energy and maintain the spatial relationship between outer shell 12 and inner shell 20.

Cords 30 are flexible cords, such as bungee cords or elastic “hold down” cords or their equivalents used to hold articles on car or bike carriers. This flexibility allows outer shell 12 to move or “float” relative to inner shell 20 and still remain connected to inner shell 20. This floating capability is also enabled by the sliding connection 22 between outer shell 12 and inner shell 20. In an alternate embodiment, sliding connection 22 may also include an elastomeric connection 22 a between outer shell 12 and inner shell 20. Padding 24 forms an inner zone and lines the inner surface of inner shell 20 to provide a comfortable material to support helmet 10 on the user's head. In one embodiment, padding 24 may enclose a loose cushioning pieces such as STYROFOAM® beads 24 a or “peanuts” or loose oatmeal.

Also seen in FIG. 3 is a cross section view of bladders 40 situated in the elastomeric zone between outer shell 12 and inner shell 20. Helmet 10 includes at least one and preferably a plurality of bladders 40. Bladders 40 are filled with fluid, either a liquid such as water or a gas such as helium or air. In one preferred embodiment, the fluid is helium as it is light and its use would reduce the total weight of helmet 10. In an alternate embodiment, bladders 40 may also include compressible beads or pieces such as STYROFOAM® beads. Bladders 40 are preferably located under apertures 14 of outer shell 12 and are in contact with both inner shell 20 and outer shell 12. Thus, if outer shell 12 is pressed in toward inner shell 20 and the user's skull during a collision, the fluid in one or more of bladders 40 will compress and squeeze bladder 40, similar to squeezing a balloon. Bladder 40 will bulge toward aperture 14 and displace elastomeric diaphragm 16. This bulging-displacement action diverts the force of the blow from the user's skull and brain up toward the aperture providing a new direction for the force vector. Bladders 40 may also be divided internally into compartments 40 a by bladder wall 41 such that if the integrity of one compartment is breached, the other compartment will still function to dissipate linear and rotational forces. Valve(s) 42 may also be included between the compartments to control the fluid movement.

FIG. 3A is a cross section view similar to FIG. 3 discussed above depicting an alternate embodiment of helmet 10. Helmet 10 in FIG. 3A includes a crumple zone formed by intermediate shell 50 located between outer shell 12 and inner shell 20. In the embodiment shown, intermediate shell 50 is close to or adjacent to inner shell 20. As seen in FIG. 3A, intermediate shell 50 encloses filler 52. Preferably, filler 52 is a compressible material that is packed to deflect the energy of a blow to protect the skull, similar to a “crumple zone” in a car. The filler is designed to crumple or deform, thereby absorbing the force of the collision before it reaches inner pad 24 and the brain case. In this embodiment, it can be seen that cords 30 extend from inner shell 20 to outer shell 12 through intermediate shell 30. One suitable filler 52 is STYROFOAM® beads or “peanuts” or equivalent material such as is used in packing objects. Because of its “crumpling” function, intermediate shell 50 is preferably constructed with a softer or more deformable materials than outer shell 12 or inner shell 20. Typical fabrication material for intermediate shell 50 is a stretchable material such as latex or spandex or other similar elastomeric fabric that preferably encloses filler 52.

FIG. 4 is a top view of one section of outer shell 12 of helmet 10 showing an alternate embodiment in which liftable lids 60 (“lid 60”) are used to cover aperture 14 to shield diaphragm 16 and/or bladder 40 from punctures, rips, or similar incidents that may destroy their integrity. Lids 60 are attached to outer shell 12 by lid connector 62 (“connector 62”) in such a way that they will lift or raise up if a particular diaphragm 16 bulges outside of aperture 14 due to the expansion of one or more bladders 40, exposing it to additional collisions. Because it is liftable, lid 60 allows diaphragm 16 to freely elastically bulge through aperture 14 above the surface of outer shell 12 to absorb the force of a collision, but still be protected from damage caused by external forces. In an alternate embodiment, diaphragm 16 is not used and lid 60 directly shields and protects bladder 40. In one embodiment, lids 60 are attached to outer shell 12 using hinges 62. In an alternate embodiment, lids 60 are attached using flexible plastic attachment 62.

FIG. 5 is an exploded view showing one method cord 30 is attached to helmet 10 to enable outer shell 12 to float over inner shell 20. Cavities 36, preferably with concave sides 36 a, are drilled or otherwise placed in outer shell 12 and inner shell 20 so that the holes are aligned. Each end of cord 30 is attached to plugs 32 which are then placed in the aligned holes. In one embodiment, plugs 32 are held in cavities 36 using suitable adhesives known to those skilled in the art. In an alternate embodiment, plugs 32 are held in cavities 36 with a friction fit or a snap fit.

FIG. 5A is a cross section of the completed fitting in which cord 30 is attached to two plugs 32 and extends between outer shell 12 and inner shell 20. Also seen is intermediate shell 50 enclosing filler 52. Not seen are bladders 40 which would be situated between intermediate shell 50 (or inner shell 20) and outer shell 12.

Thus it is seen that the objects of the invention are efficiently obtained, although changes and modifications to the invention should be readily apparent to those having ordinary skill in the art, which changes would not depart from the spirit and scope of the invention as claimed. 

1. A protective helmet having multiple protective zones comprising: an impenetrable outer protective zone formed by a hard outer shell, said hard outer shell including a plurality of apertures; an anchor zone formed by a hard inner shell; an inner zone formed by a padded inner liner functionally attached to said hard inner shell; and, an elastomeric zone formed a plurality of fluid-filled bladders positioned between said outer shell and said padded inner liner and a plurality of elastomeric cords extending between and connecting said outer shell and said inner liner.
 2. The protective helmet as recited in claim 1 wherein said fluid in said fluid-filled bladder is a gas.
 3. The protective helmet as recited in claim 2 wherein said fluid is helium.
 4. The protective helmet as recited in claim 2 wherein said fluid is air.
 5. The protective helmet as recited in claim 1 wherein said fluid is a liquid.
 6. The protective helmet as recited in claim 5 wherein said fluid is water.
 7. The protective helmet as recited in claim 1 further comprising a face protection device.
 8. The protective helmet as recited in claim 7 wherein said face protection device is a visor.
 9. The protective helmet as recited in claim 7 wherein said face protection device is a face mask.
 10. The protective helmet as recited in claim 7 further comprising at least one first elastomeric connector connecting said face protection device to said helmet.
 11. The protective helmet as recited in claim 1 further comprising elastomeric diaphragms over said plurality of apertures.
 12. The protective helmet as recited in claim 11 further comprising at least one liftable lid covering said elastomeric diaphragms.
 13. The protective helmet as recited in claim 1 further comprising at least one liftable lid covering said plurality of apertures.
 14. The protective helmet as recited in claim 1 further comprising a crumple zone between said outer shell and said inner shell wherein said crumple zone includes intermediate shell enclosing cushioning pieces.
 15. The protective helmet as recited in claim 14 wherein said plurality of elastomeric cords passes through said intermediate shell.
 16. The protective helmet as recited in claim 1 wherein said inner padding is filled with cushioning pieces.
 17. The protective helmet as recited in claim 1 further comprising a sliding connection between said outer shell and said inner shell.
 18. The protective helmet as recited in claim 1 further comprising a second elastomeric connector connecting said outer shell and said inner shell.
 19. The protective helmet as recited in claim 18 wherein said second elastomeric connector is u-shaped.
 20. The protective helmet as recited in claim 1 further comprising a chin strap.
 21. The protective helmet as recited in claim 1 wherein said plurality of apertures in said outer shell is replaced by a plurality of interstial spaces between said fluid bladders, wherein said fluid bladders expand into at least one of said plurality of interstial spaces between said outer shell and said inner shell when said helmet is struck by a linear or rotational force.
 22. The protective helmet as recited in claim 1 wherein at least one of said plurality of fluid-filled bladders is positioned under at least one of said plurality of apertures.
 23. A protective helmet having multiple protective zones comprising: an impenetrable outer protective zone formed by a hard outer shell, said hard outer shell including a plurality of apertures; an anchor zone formed by a hard inner shell; an inner zone formed by a padded inner liner functionally attached to said hard inner shell; a crumple zone between said outer shell and said inner shell wherein said crumple zone includes intermediate shell enclosing cushioning pieces and, an elastomeric zone formed a plurality of fluid-filled bladders positioned between said outer shell and said inner liner and a plurality of elastomeric cords extending between and connecting said outer shell and said inner liner.
 24. The protective helmet as recited in claim 23 wherein said fluid in said fluid-filled bladder is a gas.
 25. The protective helmet as recited in claim 24 wherein said fluid is helium.
 26. The protective helmet as recited in claim 24 wherein said fluid is air.
 27. The protective helmet as recited in claim 23 wherein said fluid is a liquid.
 28. The protective helmet as recited in claim 27 wherein said fluid is water.
 29. The protective helmet as recited in claim 23 further comprising a face protection device.
 30. The protective helmet as recited in claim 29 wherein said face protection device is a visor.
 31. The protective helmet as recited in claim 29 wherein said face protection device is a face mask.
 32. The protective helmet as recited in claim 29 further comprising at least one first elastomeric connector connecting said face protection device to said helmet.
 33. The protective helmet as recited in claim 23 further comprising elastomeric diaphragms over said plurality of apertures.
 34. The protective helmet as recited in claim 33 further comprising at least one liftable lid covering at least one of said elastomeric diaphragms.
 35. The protective helmet as recited in claim 23 further comprising at least one liftable lid covering at least one of said plurality of apertures.
 36. The protective helmet as recited in claim 23 wherein said inner padding is filled with cushioning pieces.
 37. The protective helmet as recited in claim 22 further comprising a sliding connection between said outer hell and said inner shell.
 38. The protective helmet as recited in claim 23 further comprising a second elastomeric connection connecting said outer shell and said inner shell.
 39. The protective helmet as recited in claim 38 wherein said second elastomeric connection is u-shaped.
 40. The protective helmet as recited in claim 23 further comprising a chin strap.
 41. The protective helmet as recited in claim 23 wherein said plurality of apertures in said outer shell is replaced by a plurality of interstial spaces between said fluid bladders, wherein said fluid bladders expand between said outer shell and said inner shell when said helmet is struck by a linear or rotational force.
 42. The protective helmet as recited in claim 23 wherein at least one of said plurality of fluid-filled bladders is positioned under at least one of said plurality of apertures 